Filing dc and ny taxes - on NY form it says to file DC first, on DC form it says to file NY first. What do I do?

When I go to do my nonresident state form (DC), it takes me to a screen that says “summary of taxes paid to other states.” NY is listed on this screen, but the amount says $0. 

When I hit edit, it takes me to a screen that says “be sure to finish the other state’s return before completing this section.” 

If I hit continue to the next screen anyway, it asks me to “enter the income taxed by both DC and NYC, and the taxes you paid to New York.” There’s a box for “double-taxed income” and a box for “tax paid to New York on double-taxed income.” 

I don’t know what to enter or what to do because I haven’t filled out my NY form yet, per my message above.